In recent years, development of oxide-based superconductors has been energetically made, but, because of a poor processability of the oxide-based superconductors, it has become important to study how practically useful wires, thin films or sheet materials are to be prepared. Conventional methods of preparing superconductors include a sputtering process in which superconductor starting materials are fired and ground into powder, followed by press molding, and the resulting material is sputtered on a substrate; a screen printing process in which superconductor starting materials are fired, ground into powder, and thereafter kneaded into a paste, which is screen printed on a substrate; and a solvent coating process in which superconductor starting materials are fired, ground into powder, and thereafter dispersed in a solvent, which is coated on a substrate.
However, although the sputtering process can prepare superconductors with a uniform thickness regardless of the shape of the substrate, they are greatly affected by the properties of the substrate, at the same time resulting in compositional differences between sputtering materials and products, and also resulting in a poor continuous workability. On the other hand, the screen printing process or solvent coating process has no such problems, but can not yield superconductors with a uniform thickness if the substrate has irregularities, and also preliminary drying must be carried out to substantially completely remove the solvent in carrying out re-firing.